docs: def get_deep_attr(obj, keys):
      """ Helper for DeepKey"""
      cur = obj
      for k in keys:
          if isinstance(cur, Mapping) and k in cur:
              cur = cur[k]
              continue
          else:
              try:
                  cur = getattr(cur, k)
                  continue
              except AttributeError:
                  pass
          raise DataError(error='Unexistent key')
      return cur